Still from American Sniper. The comic is never named, but if you look closely, you can see that it's issue No. 1 of the sixth volume of Punisher, released in January of 2004 (making it very believable as something Biggles could be reading during the platoon's 2004 deployment).
A Dr. Garry Choy, MD, Diagnostic Radiology, answered. Radiation fibrosis is the result of prior radiation exposure that results in scarring of an organ such as breasts, lungs, etc. Post radiation treatment fibrosis is the typical cause.
The relationship between pulmonary scarring and lung cancer was specific to the same lung and extended over time, the study authors write. These findings are consistent with the hypothesis that localized inflammatory processes associated with scarring promote the subsequent development of lung cancer..